BEIRUT, Lebanon (AP)—Shiite Moslem militiamen withdrew Wednesday from all positions ringing Palestinian refugee camps in Beirut, ending a nearly 3-year-old siege.

Syrian troops immediately rolled into buffer zones around the Chatilla and Bourj el-Barajneh shantytowns to enforce the newly established peace between guerrillas of Yasser Arafat’s Palestine Liberation Organization and militiamen of Lebanese Justice Minister Nabih Berri’s Amal.

Reporters saw Amal irregulars pull away in trucks and jeeps from sandbagged positions and earthmounds surrouding the two camps, home for an estimated 30,000 refugees.

The move came to enforce a decision declared by Berri on Saturday to lift the military blockade in what he called a unilateral initiative to end the so-called “camps war” that had killed more than 1,600 people and wounded 3,600 by Lebanese police count.

Berri said his move was a gift to the “heroic people” who have been protesting Israel’s occupation of the West Bank and Gaza Strip.

The Shiite withdrawal brought the two Beirut refugee camps under the direct control of the Syrian army, which deployed a 7,500-strong contingent in the Moslem sector of the Lebanese capital last year to curb militia fighting.

The force at the two camps was estimated at 1,300 Syrian troops. They took up positions in 17 battle-scarred buildings overlooking the interior of the shantytowns and the Shiite slums surrounding them.

Amal besieged the camps in Beirut in May 1985 to prevent Arafat from rebuilding the power base he lost in Israel’s 1982 invasion of Lebanon. Amal relaxed a food blockade of the Chatilla and Bourj el-Barajneh last April, but its militiamen continued to ring the Beirut shantytowns, preventing men from leaving.

Amal spokesmen, speaking on condition of anonymity, said men would be allowed to move freely in and out of the two camps as of Thursday.